The present invention relates to a surfactant that is soluble in an acidic aqueous medium, such as an acidic aqueous emulsion of polymerization medium as described below. This surfactant is useful as an emulsifier, particularly as an emulsifier for the preparation of latex polymers, for example, the latex polymerization of vinyl acetate.
The copolymers of the present invention have a very low level, compared to compounds of the prior art, of ethylenically unsaturated monomer which contains a sulfonic acid (or its salt) substituent. The use of such low levels of the sulfonate containing monomer is advantageous since such monomers are expensive.